In general, a suspension system for a vehicle is an important apparatus for achieving riding quality and running stability, and mainly serves to suppress or quickly reduce vibration transmitted from wheels while stably supporting a vehicle body from the wheels.
A lower arm, which serves to connect and support the wheels to the vehicle body, is used in the suspension system, and a geometry bush is mounted on the lower arm so as to perform very important functions of improving vibration transmission characteristics of the vehicle or riding quality and driving stability of the vehicle by mitigating vibration and impact generated from an uneven road surface.
Recently, a fluid filled type bush is used instead of a general geometry bush that simply includes an outer pipe, an inner pipe, and an insulator.
In this regard, Korean Patent No. 10-0974593 discloses ‘Fluid Filled Type Bush’. As illustrated in FIG. 1, the fluid filled type bush includes a damping unit 20 disposed between an outer pipe 3 and a stopper 9 of an insulator 7 in which a flow path is formed, and is characterized by preventing direct contact between the outer pipe 3 and the stopper 9 when excessive impact force occurs when the vehicle moves, reducing impact force, and improving riding quality.
Hereinafter, in describing the fluid filled type bush, names of constituent elements are consistently used in order to clearly describe a difference from a hydro bush according to the present invention.
When describing a hydro bush 2 in the related art with reference to FIGS. 2 to 5, the hydro bush 2 includes an outer pipe 30, an inner pipe 40 which has a plunger 41 that protrudes at one side of an outer circumferential surface of the inner pipe 40, a rubber portion 50, and stoppers 60 which are installed at both side ends of the inner pipe 40. An arrow illustrated in FIG. 5 indicates a flow of a working fluid that flows along flow paths 52.
The rubber portion 50 is installed between the outer pipe 30 and the inner pipe 40 that is installed in the outer pipe 30, and has a liquid chamber 51, and the flow paths 52 that are connected to the liquid chamber 51, as illustrated in FIGS. 3 to 5. Here, the liquid chamber 51 is formed concavely in a circumferential direction of the rubber portion 50, and the interior of the liquid chamber 51 is filled with a working fluid.
The flow paths 52 are formed as grooves in an outer circumferential surface at edges of both side ends of the rubber portion 50 in the circumferential direction, and connected to the liquid chamber 51. Accordingly, the working fluid more stably absorbs impact force, which is transmitted from the vehicle when the vehicle moves, using damping force.
Meanwhile, as important design factors that determine dynamic characteristics of the hydro bush 2, there are a length of the flow path 52 along which the working fluid flows, and a size of the liquid chamber 51.
Therefore, it is difficult to secure a sufficient length of the flow path 52 under a condition in which there is a limit on the size of the hydro bush 2 due to a package restriction of the vehicle, and in a case in which the length of the flow path 52 is increased, the size of the liquid chamber 51 is decreased, and the functions of the hydro bush 2 are restricted.
That is, in a case in which when the rubber portion 50 is designed, the length of the flow path 52 is increased in order to tune dynamic characteristics, while securing the flow paths 52 having predetermined widths at both sides of the rubber portion 50, as illustrated in FIG. 4, there is a problem in that the size of the liquid chamber 51 is reduced.
Accordingly, there is a need for a structure that may secure a maximum length of the flow path 52 and a sufficient size of the liquid chamber 51.